disable touchpad while typing has no effect

cinnamon --version: Cinnamon 4.4.8
Distribution: Linux Mint 19.3 Tricia 5.3.0-42-generic x86_64

Issue
Cinnamon Settings => Mouse and Touchpad => "Disable touchpad while typing" has no effect. I daily have the issue, that I am typing and hit the touchpad with my thumb, thereby selecting text up to the mouse pointer and then overwriting my text.
Usually I can solve it by ctrl+z but it is super annoying and is a huge distraction from my work.

Steps to reproduce
Probably you need to use the same driver as me. xserver-xorg-input-synaptics, xserver-xorg-input-libinput and xserver-xorg-input-all. Also, xserver-xorg-input-wacom is installed but I do not think it matters.

cat /proc/bus/input/devices:

I: Bus=0011 Vendor=0002 Product=0007 Version=01b1
N: Name="SynPS/2 Synaptics TouchPad"
P: Phys=isa0060/serio1/input0
S: Sysfs=/devices/platform/i8042/serio1/input/input5
U: Uniq=
H: Handlers=mouse1 event6 
B: PROP=15
B: EV=b
B: KEY=e520 10000 0 0 0 0
B: ABS=660800011000003

Press any character key and move the mouse via the touchpad while pressing (holding or repeatedly pressing).

Expected behaviour

Touchpad should be disabled while pressing any other key on the keyboard. And at least for 500ms.

Other information

Not sure if this is a problem in the settings file or if it is upstream.

Start with files/usr/share/cinnamon/cinnamon-settings/modules/cs_mouse.py and reproduce the issue using the listed Synaptics and libinput drivers. Determine whether the setting is applied by Cinnamon or must be handled upstream, then verify that the touchpad is disabled for at least 500ms while keyboard input is active.